I upgraded to Quantic yesterday; it runs on a Macbook Pro.
After using boot-repair to be able to boot to Ubuntu (via live CD), I found myself without any connection to Internet, be it with ethernet or wireless.

When I try a ping ubuntu.com from the default Ubuntu terminal, the only answer I get is ping: unknown host ubuntu.com.

Here is a list of facts:

The computer is a macbook pro ("MacBookPro3,1" with sudo dmidecode -s system-product-name);

Internet is provided through a router (with Tomato on it);

Local network works fine: I can ping other devices, mount NAS volumes via fstab, etc.

Other devices can connect to Internet; this is how I can write this question.

I searched on askubuntu.com and other websites, but everything I tried end up with no luck.

I don't exactly know why this file would have changed while upgrading to 12.10. Maybe some other logic has changed and this was a side effect; I can't tell.
You can try this out first if you encounter a similar problem though.